1. Field of the Invention
The present invention relates to a copying paper feeding device of an intermediate tray for use in a copying machine with functions of both-side copy, composite copy, etc. and which unit, in particular, contributes to a solution of failure in paper feed.
2. Description of the Prior Art
FIG. 2 is a schematic cross sectional side view showing an example of a photocopying machine wherein the both-side copying can be achieved as described above, and FIG. 3 is a view showing in detail part of a copying paper feeding device in an intermediate tray in the copying machine.
As illustrated by these drawings, paper supply cassettes 4, 5, 6 are received by the machine body 3. For example, when a paper to be copied, which has been transported from said paper supply cassette 6 by means of a supply roller 7, passes near a photosensitive drum 9 through a transport device 8, a toner image formed on the surface of said photosensitive drum 9 is transferred to the paper.
Then, the paper is fed by a conveyor belt 10 to a fixing roller 11. The paper on which the toner image has been fixed by the fixing roller 11 is discharged by a discharge roller 12 to a discharge tray not shown, when the paper is not subjected to processing for double-side copying.
If the double-side copying operation is conducted, after passed through said fixing roller 11, the paper reaches a switch-back member 13, where the paper is turned to run through separating trays 14a, 14b down to an intermediate tray 15.
A push-out roller 20 is provided downstream of the intermediate tray 15 relative to the direction in which the paper is fed and at the leading end of a lever (not shown) which is tossable around a shaft 16 as shown in FIG. 3. This push-out roller 20 is pressed by its own weight against a friction plate 21 mounted on the bottom of said intermediate tray 15.
There is provided as pointed by an arrow 22 a stopper 23 bendably on the place downstream of the intermediate tray 15. A friction plate 26 is mounted on a curved passage 25 for paper which starts from said stopper 23 via a feed roller 24 to said transport device 8. A roller 27 in slidable contact with the friction plate 26 and said push out roller 20 are connected with each other by a belt 28 in such a manner that the both rollers may rotate together.
Said push-out roller 20 is separated from the intermediate tray 15 by a pin 29 mounted on said lever not shown which is pushed upward by a solenoid 30 each time the paper is discharged one by one by the push-out roller 20.
In the vicinity of said push-out roller 20 are provided a slit plate 31 and a photointerrupter PI. The slit plate 31 is put in contact with the surface of the copying paper delivered out by the roller 20 and driven by the paper into rotary motion. The photointerrupter PI is intended to measure the delivery rate of paper being copied, by counting the number of a pulse of a light beam running through said slit plate 31.
In this connection, after being fed into the intermediate tray 15 via the separating trays 14a, 14b, the paper is pushed forward by the push-out roller 20 in action with the leading end of the paper inserted the nip portion of between said friction plate 21 and the roller 20. The control of the delivery rate of the paper to be fed is performed by counting the number of rotations of the slit plate 31 in response to a signal from said photointerrupter PI. However, with the slit plate 31 having adjacent slits not closely spaced, the arrangement is such that by rotating the pushout roller 20 for a certain period of time only after a determined number of pulses from the photointerrupter PI has been inputted, the paper is pushed forward for a predetermined length.
The paper thus delivered is abutted by its leading end on the stopper 23 and the paper will be maintained more or less flexed between the roller 20 and the stopper 23. At the point of time, the push-out roller 20 stops its rotation, which the operation of the solenoid 30 follows to lift the push-out roller 20. This releases the paper from its flexed position with its leading end in contact with the stopper 23. Subsequently, the solenoid 30 is actuated again, and the push-out roller 20 will next on the paper so that the latter will be interposed between the push-out roller 20 and the friction plate 21 against the following supply of a paper being copied.
When a set number of sheet of papers are supplied to the intermediate tray 15, the stopper 23 is swung in a retractive direction or in a direction in which it will fall down. And then the push-out roller 20 is rotated to send out to the feed roller 27 a sheet of paper located on the top of a stack of the papers.
The supply roller 27 delivers to the feed roller 24 along the passage 25 the paper which has been transported under the control of the friction plate 26 preventing the paper from accompanying other papers. The feed roller 24 further sends out the paper to the transport device 8. After passing through the feed roller 24, the paper runs through the photosensitive drum 9 to undergo the copying process on its reverse side, then travelling with the conveyer belt 10 via fixing roller 11, and discharge roller 12 before it is discharged from the machine.
Said push-out roller 20 is adapted to send out the paper once processed for copying as it is in contact with the surface of the paper, and therefore, the paper must not be pressed so hard by the push-out roller 20 lest the surface of the paper should become stained. For this purpose, said push-out roller 20 is so designed that while supported by the tossable lever, it will be moderately pressed on the surface of the paper by its own weight. However, if a large number of papers are supplied, said lever on which the pushout roller 20 is mounted will be inclined to a greater extent that the pressure force applied to the copying paper will be diminished. This makes it impossible to obtain a necessary and sufficient delivery rate of paper. Such a trend would be more remarkable with the papers forming top layers of the stack of papers introduced into the intermediate tray 15. Above all, some paper has a low coefficient of friction in its nature; such a paper can not be pushed out sufficiently, and so when it gets in contact with the stopper 23, a proper amount of flex is hardly obtainable. For this reason, there may occur a lack in delivery rate in case of a paper having a especially low coefficient of friction.
When additional papers are brought in, some of the papers located in the comparatively lower section of a stack of papers on the intermediate tray 15 may be advanced to a certain degree accordingly, whereby the above-described shortage of delivery rate made by the push-out roller 20, if any, would never create a big problem. Contrary to this, since none of the papers on the uppermost layer will ever been moved out accompanied by the papers forming the upper layers, the delivery shortage is most likely to be particularly considerable.